In aircraft of the prior art, an alteration to the layout of an aircraft cabin generally requires changing the air distribution and the temperature regulation of the aircraft air-conditioning system. Such a change is costly and time-consuming. In an aircraft air-conditioning system of the prior art, a stream of cold, pre-conditioned air is tapped off in order to supply different zones of an aircraft cabin. The individual blow-in temperature of separate zones is determined by heating devices. Such heating is devices may, for example, be trim valves which are also denoted as trim air valves (TAV). To reach a pleasant temperature in the respective zones, it may be necessary that air at different temperatures is supplied to the zones. The thermal loads in one zone are, for example, determined by the passenger density thereof and the electronic entertainment devices present therein For example, in a zone with few passengers a higher blow-in temperature is required than in a zone with many passengers.
The division and the size of the zones, for example for first class, business class and economy class, are partially altered at short notice by the users of the aircraft, i.e. according to the respective need. If the boundary of a zone is displaced, in order for example to increase the size of business class, in the prior art it is also necessary to modify the air distribution system. The transition of the different blow-in temperatures should take place as accurately as possible at the boundary of the two zones, so that the air stream adapted to the passenger density may also be made available to the passengers in the transition region.
The alteration to the length of a zone involves a considerable cost. The air outlets of both zones have to be modified. Moreover a further calibration of the entire air distribution system, for example by means of deflection plates, is required as the pressure ratios and volumetric flows are altered. Already at the aircraft design stage, supply lines to the two zones have to be designed respectively according to the largest configuration, i.e. the largest required supply line diameter has to be used.
The heating devices, for example the trim valves, have to be designed respectively for the largest configuration of the zone.
FIG. 1a and FIG. 1b show an aircraft cabin with a first zone 106a and a second zone 106b of variable length. The first zone 106a comprises a zone temperature sensor 116a, and the second zone 106b comprises a second zone temperature sensor 116b. In the first configuration 102 according to FIG. 1a, the first zone 106a is shorter than the second zone 106b. A first air supply line 110a, a first trim valve 108a and a first temperature sensor 112a are associated with the first zone 106a. A first distribution line 114a comprising a plurality of air outlets distributes the air supplied to the first zone 106a. A second air supply line 110b, a second trim valve 106b and a second temperature sensor 112b are associated with the second zone 106b. A second air distribution line 114b comprising a plurality of openings distributes the supplied air in the second zone 106b. 
FIG. 1b shows a second configuration 104 in which the first zone 106a has been enlarged and the second zone 106b has been accordingly shortened. To this end, the length of the first air supply line 114a has been lengthened and the length of the second air supply line 114b has been shortened. As a result, in the second configuration 104 a greater air volume flows through the first air supply line 110a compared with the first configuration 102, whilst in the second configuration 104 a smaller air volume flows through the second air supply line 110b compared with the first configuration 102. This requires, for example, a re-calibration of the aircraft air-conditioning system and/or of the air distribution system, which is time-consuming and susceptible to error.